Rare. Known from several water bodies in the valleys of western Montana. Additional information on the species is needed within Montana to more precisely determine the species' conservation status.

General Description

Columbia Water-meal, a minute floating aquatic perennial, is among the world's smallest flowering plants. The plant body is rootless and thalloid, with no distinction between stem and leaf. The symmetrical, globular, uniformly green thalli are less than 1.5 mm long, smooth and rounded on the back, and floating just below the surface of the water. The plants rarely flower and for the most part reproduce vegetatively by budding. They often grow in large colonies.

Species of Wolffia are distinguished from other genera of small floating aquatics in the duckweed family (Lemna, Spirodella, Wolffiella) by their smaller size, and by being both globose and rootless.Wolffia columbiana is distinguished from other Wolffia by the upper surface of its thallus, which is rounded and smooth (sometimes with minute humps) rather than flattened and/or with sunken brown dots.